New clue to depression

THURSDAY, July 8 -- Low brain levels of the inhibitory transmitter GABA and high levels of the excitatory neurotransmitter glutamate seem to be strongly associated with melancholic depression, says a Yale University study in the current issue of the Archives of General Psychiatry.

Melancholic depression is a common form of depression. Its symptoms include insomnia, loss of appetite and loss of pleasure.

"Depressed subjects with melancholic features appear to have the largest and most consistent GABA reductions," research leader Gerard Sanacora, director of the Yale Depression Research Program, said in a prepared statement.

"This also appears to be especially clear in the subset of melancholic subjects who also have psychotic features. In contrast, normal or near normal GABA concentrations were found in the majority of atypically depressed subjects," Sanacora said.

He and his colleagues used proton magnetic resonance spectrometry to record the levels of GABA and glutamate in 33 people with major depression and 38 healthy people.

The findings could help doctors more accurately diagnosis depression and provide more effective treatment.

"At the moment, we have limited ability to predict how a patient will respond to one treatment for depression compared to another," Sanacora said.

"We are very interested in exploring the usefulness of these and other biological markers in identifying various subtypes of depression and predicting specific treatment responses," he said.